Japanese Numbers
How to count from 1 to a billion in Japanese. The two reading systems, the counters, and the big four irregularities.
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- Number systems
- 2 (native + Sino-Japanese)
- Counters in active use
- ~350, but 10 cover daily life
- Safe fallback counter
- -tsu (hitotsu, futatsu...)
- Critical irregulars
- 4, 7, 9 each have two readings
The two systems
Wa-go (native Japanese): hitotsu, futatsu, mittsu, yottsu, itsutsu, etc. Used for objects up to 10. Falls out of use beyond that.
Kan-go (Sino-Japanese): ichi, ni, san, shi, go, roku, shichi, hachi, kyū, jū. This is the system used for everything else. Counts up cleanly into the millions and billions.
Both systems coexist for 1-10. You'll hear both in real Japanese: hitotsu (one thing) vs ichi (the number 1). Beyond 10, kan-go takes over completely.
The four irregular readings
4 has two readings: yon (native) and shi (Sino-Japanese, also the word for death, usually avoided). Yon is the safer default.
7 has two readings: nana (native) and shichi. Nana is the safer default in counting.
9 has two readings: kyū (default) and ku (used in 9 o'clock and September, 九月 kugatsu). Kyū is the safer default.
0 is rei (formal) or zero (English loan). Both are common.
Counters
Japanese requires counter words attached to numbers depending on what you're counting. People use -nin (一人 hitori, 二人 futari, 三人 sannin). Long thin objects use -hon (鉛筆一本 enpitsu ippon, one pencil). Flat objects use -mai. Small animals use -hiki. Large animals use -tō.
Start with common counters for people, days, months, hours, minutes, ages, floors and general things. The generic counter -tsu (hitotsu, futatsu) can be used for some objects.
Related reading
Common questions
How do I say my age in Japanese?
Use the -sai (歳) counter: 25-sai is twenty-five years old. The exception is 20, which is hatachi (二十歳). Hatachi is a fixed reading you have to memorize.
How do I count days vs days-of-the-month?
Day-of-the-month: tsuitachi (1st), futsuka (2nd), mikka (3rd)... up to 10, then jūichi-nichi (11th), jūni-nichi (12th)... Numbers of days: ichinichi (1 day, irregular), futsuka (2 days), mikka (3 days)... Same readings, different meaning by context.
Are Japanese numbers used in math?
Mostly Sino-Japanese (ichi, ni, san) for arithmetic. Native readings (hitotsu, futatsu) appear in counting objects but not in equations. Computer programming and academic math use Sino-Japanese.
